Fluid flow control valves are known which use flexible, resilient diaphragms for sealing against a valve seat. The diaphragm flexes away from the valve seat to open the valve and allow fluid to flow between the valve inlet and outlet. Typically, an annular peripheral rim portion of the diaphragm is clamped between two mating portions of the valve to support the diaphragm in the valve. U.S. Pat. No. 4,505,450 to Saarem discloses such a valve in which the diaphragm rim is clamped between the valve body and a separable cap therefor.
In most valves of this type, including the Saarem valve, the diaphragm rim is tightly compressed to prevent leakage between the diaphragm and the mating valve portions. Saarem uses an open-ended nut which can be screwed down to force the cap against the valve body and thereby compress the diaphragm rim. Other known valves use a plurality of spaced, threaded bolts which extend through the mating valve portions. These bolts can be sufficiently tightened using a wrench to compress the diaphragm rim.
However, it is desirable, for manufacturing and service reasons, to have a valve in which the mating portions that clamp the diaphragm rim are simply screwed together by hand, without using a wrench or other tools. It is faster and easier to assemble or disassemble such a valve and it is not necessary to have any tools on hand. Unfortunately, various problems are presented in achieving an adequate seal with prior art diaphragm rims. For one thing, it is difficult to sufficiently compress the rim, using just hand tightening, to achieve an adequate compression seal. In addition, the relative rotary motion at the interface between the mating valve components can pinch or deform the diaphragm rim causing the diaphragm to leak.